1. Field of the Invention
The invention relates to a fuel injector with a holding body and a nozzle body.
2. Description of the Prior Art
DE 196 50 865 A1 has disclosed a solenoid valve for controlling the fuel pressure in a control chamber of an injection valve, for example in a common rail/high-pressure accumulator injection system. The fuel pressure in the control chamber is used to control a stroke motion of a valve piston by means of which an injection opening of the injection valve is opened or closed. The solenoid valve includes an electromagnet, a movable armature, and a valve element that is moved by the armature, is acted on in the closing direction by a valve closing spring, and cooperates with the valve seat of the solenoid valve, thus controlling the flow of fuel out of the control chamber.
In fuel injectors that have been used up to this point, a screw connection is produced by means of a clamping nut, which connects a nozzle body, a throttle plate resting against it, and a valve plate of the fuel injector to the holding body of the fuel injector. Firstly, it is of secondary importance whether the fuel injector is actuated by means of a piezoelectric actuator or by means of a solenoid valve. In general, a sealing ring preferably made of PTFE is used to seal the low-pressure region of the fuel injector in relation to the outside. In order to attach the nozzle clamping nut—which as a rule encompasses a nozzle body, a nozzle plate, and a valve plate—to the holding body, a thread is embodied on the inside of the nozzle clamping nut. By means of this thread, the prestressing force produces a screw-connected assembly composed of the holding body and nozzle body as well as the components inserted between them. The production of the thread on the inside of the nozzle clamping nut on the one hand and on the outer circumference surface of the holding body on the other hand is complex and expensive; in addition, an undesirable leakage can occur at the thread and an unevenly distributed action of the prestressing force introduced into the screw-connected assembly by the clamping torque of the thread.
In fuel injectors, couplers are used, which are as a rule modularly embodied and extend between a switching valve of the fuel injector and an actuating element, whether the latter is a solenoid valve or a piezoelectric actuator. The coupler modules previously used in fuel injectors include an open spring sleeve, which is contained in the coupler module and subjected to powerful dynamic stresses during operation and therefore must be embodied in a very rugged fashion.
Previous embodiment versions of a spring sleeve inserted into the coupler module include annularly arranged holes that extend in alternatingly situated patterns of holes. The spring sleeve is embodied, for example, in the form of an open spring sleeve and has two different stamping geometries, which assure that the open spring sleeve remains free of transverse forces when it is placed under axial stress.
During injector operation, individual differential distances d1 through d7 are produced, which differ from one another when subjected to dynamic stress as opposed to static stress. They vary in a chronological sequence. Under a static load, the differential distances d1 through d7 are the same size as one another and each correspond to a fraction of the total length of the spring sleeve.
The differential distances and the connected local dynamic stress is significantly higher in the edge region of the for example open spring sleeve and decreases toward its middle. An optimized embodiment of the as a rule open spring sleeve makes it possible to increase the ruggedness, i.e. the number of stress cycles that can be endured without damage.